Understanding UV‐Induced Degradation Mechanisms in SHJ Solar Cells and Their Reversibility: The Role of Hydrogen and Doping

ABSTRACT Silicon heterojunction solar cells are among the leading PV technologies for high‐efficiency modules, but their sensitivity to UV radiation raises durability concerns for outdoor deployment. In this study, we investigate the UV‐induced degradation of silicon heterojunction cell precursors by isolating the impact of subcell layers under controlled UVA and UVB irradiations. Our results identify the front hydrogenated amorphous silicon (i/n)a‐Si:H layers as key degradation sites, exhibiting significant losses in minority carrier lifetime and iV oc ( mV). Fourier‐transform infrared (FTIR) spectroscopy indicated a selective degradation of high stretching mode Si–H n bonding configurations, creating defects at the c‐Si/a‐Si:H interface and releasing free hydrogen. These mobile and reactive hydrogen species intensely degrade both passivation mechanisms (chemical and field‐effect) by electrically inhibiting dopants via P–H complex formation. Light soaking treatments combining thermal and light activation enable significant passivation and conductivity recovery through hydrogen redistribution, though reversibility diminishes at high UVA doses, indicating a photon‐dose‐dependent degradation threshold. These findings provide mechanistic insights into UVID pathways and highlight the importance of hydrogen management and UV attenuation strategies for long‐term SHJ module reliability.